Liquid crystal material is a mixture of organic rod-shaped small molecular compounds which has both liquid fluidity and anisotropy of crystal in a certain temperature. Because of its optical anisotropy and dielectric anisotropy characteristics, liquid crystal material is widely used in the liquid crystal display elements of the devices of electronic calculators, car dashboard, televisions, computers and the like. Based on the LCD modes, liquid crystal compositions can be classified into the types of twisted nematic (TN), super twisted nematic (STN), thin film transistor (TFT), guest-host (GH), dynamic scattering (DS) and the like. The most common display element therein is based on the Schadt-Helfrich effect and has a twisted nematic structure.
Liquid crystal materials are required to have good chemical and heat stability, a suitable optical anisotropy, a broader range of a nematic phase as well as the good stabilities to electric field and electromagnetic radiation. In addition, the liquid crystal materials should have low viscosity and produce low threshold voltage and high contrast ratio in the liquid crystal cell. Since liquid crystal material is normally used as a mixture of various components, it is especially important that these components are miscible with each other. However, as the optimization of each performance parameter of the mixed liquid crystal material may result in inter-contradictory, inter-constraint and inter-influence results, it is very difficult to achieve a broader range of a nematic phase, suitable refractivity and dielectric anisotropy, as well as low-temperature storage stability at the same time. For example, the obvious defects of the liquid crystal compositions of EP0667555, EP0673986, DE19528106, DE19528107 and WO962851 are having a longer response time, lower resistivity and overhigh operating voltage. Further, poor low-temperature storage stability is also a defect of various existing liquid crystal materials.
Therefore, in the field of liquid crystal material, there is a need for novel liquid crystal compositions with improved performances. Particularly, for many types of application, liquid crystal compositions should have a suitably broader range of a nematic phase, a suitable refractivity and dielectric anisotropy, and a low-temperature storage stability.